Re: Regex: matching character which happens exactly once

Here you go, this passes all of my test cases:

/^(?(?=((?(3)(?(?!.*\3)(?(?!((?<=(?!\3).(?=(?2)).
|(?=\3)..)))(*F))))(?(?=.)(?=(.)(?1)))))(*F))/sx
[download]

Simple!*

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Re^2: Regex: matching character which happens exactly once (updated) by haukex (Archbishop) on Oct 24, 2017 at 11:24 UTC
Duh, it's actually much simpler, and this one even captures the single character(s)! (Update 2: See Variable-Width Lookbehind (hacked via recursion)) `/(.)(?!((?<=(?!\1).(?=(?2)).\|(?=\1)..))\|.*\1)/s` [download] <Reveal this spoiler or all in this thread>	[reply] [d/l] [select]
Re^2: Regex: matching character which happens exactly once by LanX (Saint) on Nov 12, 2017 at 20:28 UTC
Hauke I kept your replies on my growing to-do list but I'm realising now that I'm won't be able to "dive" into the matter again. Thanks for your help, I'm closing the case now. > Rolf, I blame you for the sleep I lost over this! And thanks for taking care of my insomnia. ;-p Honestly, while the use case is very exotic I learned a lot about the various corners of the regex features. I hope for you too! Der Weg war das Ziel! :) Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Je suis Charlie!}	[reply]